Fuse



N. J. CONRAD April 1o, 192s.

FUSE

Filed Aug. 14, .1.924

20 should not Patented Apr. 1G, 15.92%...

UNITED stares PATENT aereas-t5I oFFica.

T SCHWEITZER 6c CONRAD, OF ILLINOIS.

FUSE.

Application led August 14, 1924. Serial No. 731,954.

This invention relates to improvements in fuses and the like. I

More particularly the present invention A relates to improvements iny fuses of the Schweitzer & Conrad type and it has special reference to an improved method of and means for sealing the' terminal ferrules upon the ends ofthe tube or other enclosing members'of such devices.

In the devices of this sort the seal should be able to withstand, without leakage, severe temperature and pressure conditions which are apt to be imposed, and the problems of properly sealing the ferrules upon the tube and providin a suitable sealing substance have been di cult ones.

The sealing substance should be sufiiciently strong to provide a tight seal and prevent leakage or escape of the fuse liquid, yet it break the container or impose severe stresses upon it, especially where the same is madevof lass. l The substance should not be of such a ardness that ita will impose too severe internal stresses on the container, 26 yet a certain amount of compression or pressure between the container, sealing substance and ferrule should be provided to secure a tight seal. Among the contributing factors toward the setting up of pressure on 30 the container are the melting point and hardness of the seal, the relative expansion and f contraction of the container, seal and ferrule, and the relative volumes of the seal and the material of the ferrule.

The meltin point of the sealing substance should be suciently high that the seal will not melt or soften under the temperatures to which such devices are subject andthe sub, stance should he such that it Qwill not be readily cracked by expansion or contraction of the parts. It should not corrode under or dinary atmospheric conditions and it should be insoluble 1n carbon tetrachloride, tetrachlorethylene and otlrer carbon derivatives and fuse liquids. Where a flux is employed the sealing substance should not be corroded thereby. y

I have, according to my present invention, provided an improved sealing substance and an improved method of sealing the tube or enclosing member. I provide a substance which meets the above requirements and 'the lmethod which I employ comprises centering the tube and ferrule, heating the ferruleto expand it, pouring the molten sealing substance, settling the seal and removing any gas bubbles -from it Y before it sets and chilling or quenching the ferrule while the sealing substance is in molten condition to obtain a tight seal. The sealing substance so and method lend themselves admirably one to the other and by means of them an improved seal is produced.

In addition to the above improvements I provide an improved flux for making a tight c5 seal, although it is possible to make the seals tight without it if recautions as to cleanliness are taken. Yhe flux will not cause corrosion between the parts and it does not produce excessive amounts of gas bubbles in 7o the seal.

in order to acquaint those skilled in the art With the nature and manner of practicing the present invention I shall now describe an "1 embodiment of the invention in connection 75 with the accompanying drawings in which;

Figure 1 is a fragmentary front elevational view showing a fuse in the clamp or rack for centering or properly positioning or aligning the tube and ferrule relative each so ot er;

Fig. 2 is a vertical section through one end of the tube and the ferrule or cap, sealing base and pouring'collar .or funnel showin the step of heating-,the ferrule o-r cap; 35

ig. 3 is a similar view showing the step of pouring the seal;

F ig. 4 is an isometric view showing the step of settling the seal and removing any gas bubbles; and

Fig. 5 is a horizontal section through the tube, seal and ferrule showing the step land in plan the means for quenching the ferrule while the seal is in molten condition.

The body of the fuse selected for illustration is formed of a sleeve or tube 5 of insulating material. The particular tube shown is of cylindrical cross section and is made of glass, although it is to be understood that the particular formation may be varied and the body 5 may be of any other suitable or preferred material. Upon the ends of the tube 5 are the metal ferrules and 7. These are usually of brass or other suitable condpcting material and they form the terminals for the conducting parts contained within the tube 5 as well known in the art. The ferrules 6 and 7 are usually splayed or provided with diametrically opposite parallel flat surfaces 8 for cooperation u@ tal bars 20 in which the threaded stems 17 -heated by a heating plate with the terminal clips between which the fuse is connected.

The present inventionuis carried lout substantially the same in connection with each of the ferrules 6 and 7 and I shall therefore explain it in connection with the sealing of only one of said ferrules, for example, the base ferrule 7. The conducting parts within the tube may be connected,l between the ferrules in the usual or any preferred manner. The upper ferrule usually has a pressure .relief opening closed by a. vent cap which is adapted to be blown clear of the opening by excessive internal pressures.

According to my present invention the ferrule 7, is loosely slipped upon the end of the tube 5 and the ferrule is then set upon a block 10. This block may be warmed or 11 upon which it rests. The block 10 has a depression 12 for receiving the ferrule 7 and an upstanding rim 13 tits snugly about the ferrule. The interior of the ferrule 7 has a tapered shoulder 14 upon which the end of the tube 5 seats. This shoulder 14 centers the tube 5 within the ferrule 7 and a suitable washer 15 is preferably interposed between it and the end of the tube.

Assuming that the upper ferrule 6 has already been sealed upon the tube, an Linverted cup 16 carried by a threaded stem 17 is adjusted down over it and clamps the parts properly centered and aligned in a rack 18 comprising uprights 19 suitably mounted upon heating plate 11 and horizonare adjustably mounted coaxial vertically with ferrule receiving depressions 12 ofthe blocks 10, suitable loclf nuts 21 being provided to lock the fuse parts properly.

clamped in the rack. It is to be understood that in actual practice the rack preferably has a plurality or row of vertically aligned clamping cups 16 and blocks 10 for clamping a plurality of fuses in the rack at the same time. To secure the first ferrule upon the tube the parts may be clamped in the rack with the other ferrule loosely in place to align the parts. A split two-piece collar 25 having a flared or funnel shaped upper end 26 is then secured upon the outside of the upper end of ferrule 7 with a shoulder 28 resting upon the top edge ofv ferrule 7 so as to provide a filling funnel above the ferrule 7 The base of the ferrule 7 may then be heated by the heating plate 11 While the sides of the ferrule and collar 25 are heated by additional heaters or burners 30 and 32 (Fig. 2) which ma extend along and be common to a row o such setups. This expands the ferrule 7 and the sealing substance 35 is melted and poured as from a vessell 36 (Fig. 3) into the flared or funnel shaped upper end of collar 25-and runs in molten Pb Sn Cd Per cent Per cent Per cent Hm'd 25 50 25 Soft 33. 3 33. 3 33. 3

'or in any variation of these proportions by which the same desirable characteristics are obtained. The ingredients are preferably mixed in molten condition. The first of the above alloys will be hereinafter referred to as hard while the other will be referred to as soft. The hard alloy has been found especially suitable for sealing the types A, B, and C, Schweitzer & Conrad fuses while the soft alloy is suitable for the D sizes. the A, B and C devices are smaller in diameter and have thinner walls. The soft alloy seems to exert less pressure (less stress)l on the glass than the hard alloy and since there has actually been a tendency toward excessive breakage in the larger size tubes, the soft alloy may be used in connection therewith. The terms hard or ysoft are referred to with reference to the lead content of the alloy.

The hard or soft alloys both have a melting point of substantially 150 degrees centigrade or over and in that it is doubtful if fuses of this type ever meet an upper limit temperature higher than 100 degrees centigrade the measure of safety against melting or softening` is suicient to withstand the most severe conditions. It has been found in makingv temperature tests that due primarily to the and the vapors inside the tube, the vent will leak at about 8O degress centigrade so that the melting point of the seal is much higher than will ever be reached.

If the melting point of the seal were appreciably under 100 degrees centigrade it would be liable to melt or soften during the time that the fuse is carrying heavy current loads in the hot sun or other warm place.

There is no possibility of this with the alloy The tubes of shownV "diagrammatica-lly yloy the more stress there seems to be on the glass tubing andthe roblem of providing a softer alloy with su ciently high melting point has been a dillcult one.

The alloy seal which I provide does not show leakage between temperatures of negative degrees centigrade and plus 100 degrees cent1 rade, the upper limit test having been con ucted by placing a sealed tube containing carbon tetrachlorlde in boilin water for one or two hours. It is doubtfu if -tubes ever have vto meet this severe a requirement. The sealA holds against the heat upon exerting 50 pounds of air pressure in the tube while under water. The alloys which I provide are insoluble in carbon tetrachloride, tetrachlorethyl'ene and other carbonI derivatives and fuse liquids at temperatures between negative 50 degrees centigrade and` plus 100 degrees centigrade and they show no si of corrosion under ordina'll'y atmospheric conditions.

' he molten sealing substance 35 having been poured into the annular s ace 40 between the tube 5 and ferrule 7, t e ferrule 7 is tapped or rapped as with a bar 42 as in Fig. 4. This quickly settles the sealm substance, completely, quickly `and uniormly .distributes the sealing substance through the space 40 and removesany gas bubbles, so that there will be no pockets, passages or interstices through which leakage is possible when the seal sets. The pourin funnel or collar 25 isreferably -remove before settling the l sea ing substance.

To obtain a ti ht` seal the ferrule is then quenched or cooled while the sealing substance is in molten condition. I find that the tightness of the seal is improved by lllenching the brass parts of ferrules before e seal solidilies and the sealin substance which I have provided permits t is quenching without setting up excessive stresses and pressures on the glass tube, as it solidifies or hardens. Most sealing substances that do not require quenching of the metal parts to provide a tight seal actually exert extreme pressures or stresses upon the tube to the point offracturing the glass. By permitting quenching of the metal parts without setting up severe stresses as it hardens the sealing subaance shows that its pressure or band is folded forwardly to provide handles 62 and a portion 63 which normally urges the jaws to closed position. The jaws 6() are lined Awith felty or other suitable absorbent material 65 -which will absorb and hold a quantit when dipped tliereinto. rule or cap 7 the jaws 60 with the absorbent lining 65 are dipped into cold water and the jaws are opened and placed upon the ferrule 7 with the felt or other absorbent material against the ferrule as shown in Fig. 5,. by grasping the handles 62, pressino` them together placing the `aws about the llerrule then "close into lamp ng engagement therewith under the action of spring portion 63. The doubled thicknesses of each handle 62 may be secured together by screws, rivets or other suitable means as shown at 70.

The quenching of the ferrule while the seal is molten contracts the ferrule first and vas the seal solidies it sets up just enou h pressure or compression to provide a tig t seal between the tube and ferrule without imposing severe stresses upon the tube. Seals that do not require quenchinv have usually placed severe stresses upon t e tube when solidified. The relative coellicients of expansion and contraction of the seal, tube and ferrule are such and the Seal has sufficient fluidit or give when hard that it will not be crac ed by relative contraction and expansion ofthe parts.

The tube is preferably washed and dried and the ferrule thoroughl cleaned before sealing itupon the tube. ere precautions of this sort with referenceto cleanliness are taken a lux is not ordinarily necessary for producing a tight seal. Where these precautions with reference to cleanliness are not taken or where a flux is for any other reason desirable or necessary to produce a tight seal, I find that a mixture of lactic acid, water and alcohol in the proportions of onethird each by volume is admirably adapted for this purpose. This flux is used in limited quantities on the brass ferrule as by wiping or painting the inside of the ferrule with it and it produces a tight seal. This llux does not cause corrosion between the different part-s or elements under atmospheric conditions, it does not corrode the alloy seal and. it may be used sparingly to minimize the formation of gas bubbles in the alloy which might otherwise be excessive and if not removed or settled would cause leakage. l

The quenching of the ferrule in the manof cold water, for example,

To quench the fersusA ' or lsevere stresses 1n the tube but they provide'sliicie'nt compression between the parts to form a tight seal. by be subject only to the contraction stresses of the seal and not to the greater or more severe contraction stresses of the errule'. j

"lido n ot intend toy be limited to the precise details or proportions shown and described,

and lnt'end that modifications in the many" ner -and order of practicing the various steps tin and cadmium proportioned to provide,

such vas will be apparent at once to those skilled in the art are contemplated within the scope of the appended claims.

I claim.

ljIn a device of the class described, the combination of a container, a fer-rule therefore, anda seal between the ierrule` and container, said seal comprising an alloy of lead,

a melting'pointL of substantially 100 degrees centigrade or over and a hardness under for said' seal. y

'2.y In av device 'of .the class described, a

i container having parts of glass and metal seale'dvtoget-her by an alloy composed entirely of lead,'ti n' and cadmium.

3.V In adevice of the class described, a

containerhaving parts of glass and metal sealed togetherfby an alloy of lead, tin and cadmium propfortionedto provide a melting point of'sub'staitially '100 'degrees centigrade or over and-a` hardnessunder 25 lfor said $111.0' f

Lyn a device ofthe class described, the

i 4combination of a, container,a ferr'ul'e therefore, vand Vseal 'between' :said container and said i,ier 1 "1141'e,` lsaid seal comprising' a substance having agnielting point over 100 "del :L l`grzlees centigrade andl a hardness under 25.

'.5. Arlll'ie ot''sealing a metalferrule The tube seemsy there-v -ferrule upon the container,

upon a glass container whichcomprises clamping the container centered within the errule, heating the ferrule to expand it, pouring a sealing substance in molten condition between the ferrule and container and quenching the ferrule to cool it while the sealing substance is molten. f

6. The method of sealing a ferrule upon the containing casing of a device of the class described which comprises placing the heating the ferrule to expand it, introducing a sealing substance in molten condition between the ferrule and container, rapping the ferrule to settle the sealing substance and quenching the ferrule to cool it while the sealing substance is molten.

7 The method of forming. a tight joint between a brass ferrule and a glass tube, which comprises' heating the errule to expand the same, loosely inserting the tube, lin the ferrule, pouring1 an alloy of lead, tin, and cadmium into e space between the parts, and quenching the ferrule while the alloy is still hot, to contract the ferrule before the alloy solidifies.

8. The method of forming a ti ht joint between two concentric parts, oneo which is of metal and the other of vitreous material which comprises heating the metal part to eX- pand the same, loosely inserting the vitreous member into the metal member', pouring a melted alloy of lead, tin and cadmium into the spacebetween the parts, and quenching the metal parts to lcontract the same before solidification of the molten alloy.

I9. ln a device of the class described, the combination of a rangible container, a ferruletherefor, and a seal cast between said container and the ferrule, said seal comprising a substance having a melting point over 100 degrees contigrade and a hardness under 25 by the Brinell test. v 1

' ln' witness whereoLIhereunto subscribe my'nam'this 11th day of August, l1924. y NICHOLAS J. CONRAD; f 

